The present invention relates to a compound based on an alkaline-earth metal, sulphur and aluminium, gallium or indium, its method of preparation and its use as a phosphor.
At the present time there have been major developments in the fields of luminescence and electronics. As an example of such developments, mention may be made of the development of cathodoluminescent systems for new display and illumination techniques. A specific application is that of the replacement of current television screens with flat screens. These new applications require phosphors having increasingly improved properties.
Known phosphors include, in particular, alkaline-earth metal thiogallates. These products may especially be prepared by spray-drying a solution or suspension of the constituent elements of the thiogallate other than sulphur, and then by sulphurizing the spray-dried product. The products obtained in this way already have good luminescence properties.
It is an object of the invention to further improve these properties.
To this end, the compound of the invention is a compound based on at least one element A chosen from alkaline-earth metals, on at least one element B chosen from aluminium, gallium and indium, on sulphur and on a dopant capable of giving the said compound luminescence properties, and it is characterized in that it is in the form of a mixture of predominantly an AB2S4-type crystallographic phase and a B2S3-type crystallographic phase.
The invention also relates to a method of preparing such a compound, which is characterized in that it comprises the following steps:
a solution or suspension containing salts or sols of the elements A, B and of the dopant is formed, in a proportion such that the B/(A+dopant) atomic ratio is at least 2.06;
the solution or suspension is spray-dried; and
the product obtained in the previous step is sulphurized.
Finally, the invention relates to the use as a phosphor, especially in cathodoluminescence, of a compound as described above.
Further features, details and advantages of the invention will become more fully apparent on reading the description which follows and from the appended drawing in which: